1. The Technical Field
The present invention relates to food products and to processes for their preparation. In particular, the present invention provides deodorization processes for oils, especially fish oils, and the resulting deordized oils.
2. Background Art
A great deal of attention has been recently paid to the various health benefits apparently associated with consumption of fish rich in fish oil. Health benefits appear to be related to the presence of high levels of the n-3 family of polyunsaturated fatty acids. Oils containing such materials, such as fish oils, are referred to as "omega-3" oils and desirably contain high levels of n-3 fatty acids, especially eicosapentaeonoic acid ("EPA") and docosahexaenoic acid ("DHA"). Such fatty acids are called "omega-3" since the first double bond occurs in the third carbon bond counting from the end or omega position of the fatty acid.
Notwithstanding the present interest in the health benefits of fish oil consumption, nonhydrogenated fish oil generally to date has not been widely used per se or as an ingredient in processed food products for use by humans due to notorious and severe problems in odor, flavor, cholesterol level, and especially stability. Nonhydrogenated fish oils exhibit notorious instability due in part to the rapid rates of oxidative and hydrolytic rancidification. However, even if kept dry and in an oxygen limited environment, fish oils exhibit antioxidation at room temperatures leading to rapid quality deterioration.
Hydrogenated fish oils are much more stable due to the decrease in the degree of polyunsaturation and are widely used in Europe for margarine. Hydrogenation is also effective in reducing odor and flavor after deodorization. Hydrogenated fish oils have also been used in Scandinavian countries in other consumer products, e.g., baked cake. However, hydrogenation by decreasing polyunsaturation including the n-3 fatty acid component correspondingly decreases the health value of fish oil. Accordingly, it would be desirable to relaize a nonhydrogenated fish oil or food products containing such nonhydrogenated fish oils, but nonetheless of increased stability.
The principal approach taken in the art to utilize nonhydrogenated fish oil has been to employ fish oils of enhanced stability. Two broach approaches have been taken in the art to realize nonhydrogenated fish oils of enhanced stability. The first approach involves attempting to find adjuvants which can be added to finished fish oil to provide desired additional stability. For example, while the phenomenon of fish oil degradation is not completely understood, it is known, however, that oxidative rancidification is a contributing factor. Addition of known antioxidants, singly as well as commercial mixtures, some allegedly synergistic, does result in some increase in stability. However, the instability of nonhydrogenated fish oils is so great, that even addition of such materials at maximum legally permitted levels provide only modest increases in stability.
In the second approach, the art has given attention to the processing of the oil to achieve a cleaner, finished oil product. Particular attention has been given to the deodorization step in order to realize cleaner finished fish oil products. Often, the deodorization step is repeated to yield higher quality oils. Deodorization of oils by steam stripping is commonly the finishing step in edible oil processing. Indeed, deodorization is often considered a
Conventional deodorization can remove undersirable flavor and odors resulting in oils which are initially clean and bland in taste and color. After conventional deodorization, however, highly polyunsaturated oils, such as soybean and fish oils, upon standing, even in anaerobic or oxygen limited environments, revert or develop flavors which resemble their initial flavor type. In Western countries, the fishy flavor developed in fish oils is found especially offensive. Also, common deodorization can lead undesirably to loss of desirable omega-3 fatty acids. Surprisingly, the present invention provides improved deodorization processes which can yield oils exhibiting not only superior initial quality, but which exhibit remarkable stability over time against oxidation.